Function resolveIfNotPlainOrUrl

src/common.js:36–114

(relUrl, parentUrl)

var backslashRegEx = /\\/g;
export function resolveIfNotPlainOrUrl (relUrl, parentUrl) {
  if (relUrl.indexOf('\\') !== -1)
    relUrl = relUrl.replace(backslashRegEx, '/');
  // protocol-relative
  if (relUrl[0] === '/' && relUrl[1] === '/') {
    return parentUrl.slice(0, parentUrl.indexOf(':') + 1) + relUrl;
  }
  // relative-url
  else if (relUrl[0] === '.' && (relUrl[1] === '/' || relUrl[1] === '.' && (relUrl[2] === '/' || relUrl.length === 2 && (relUrl += '/')) ||
      relUrl.length === 1  && (relUrl += '/')) ||
      relUrl[0] === '/') {
    var parentProtocol = parentUrl.slice(0, parentUrl.indexOf(':') + 1);
    // Disabled, but these cases will give inconsistent results for deep backtracking
    //if (parentUrl[parentProtocol.length] !== '/')
    //  throw Error('Cannot resolve');
    // read pathname from parent URL
    // pathname taken to be part after leading "/"
    var pathname;
    if (parentUrl[parentProtocol.length + 1] === '/') {
      // resolving to a :// so we need to read out the auth and host
      if (parentProtocol !== 'file:') {
        pathname = parentUrl.slice(parentProtocol.length + 2);
        pathname = pathname.slice(pathname.indexOf('/') + 1);
      }
      else {
        pathname = parentUrl.slice(8);
      }
    }
    else {
      // resolving to :/ so pathname is the /... part
      pathname = parentUrl.slice(parentProtocol.length + (parentUrl[parentProtocol.length] === '/'));
    }

    if (relUrl[0] === '/')
      return parentUrl.slice(0, parentUrl.length - pathname.length - 1) + relUrl;

    // join together and split for removal of .. and . segments
    // looping the string instead of anything fancy for perf reasons
    // '../../../../../z' resolved to 'x/y' is just 'z'
    var segmented = pathname.slice(0, pathname.lastIndexOf('/') + 1) + relUrl;

    var output = [];
    var segmentIndex = -1;
    for (var i = 0; i < segmented.length; i++) {
      // busy reading a segment - only terminate on '/'
      if (segmentIndex !== -1) {
        if (segmented[i] === '/') {
          output.push(segmented.slice(segmentIndex, i + 1));
          segmentIndex = -1;
        }
      }

      // new segment - check if it is relative
      else if (segmented[i] === '.') {
        // ../ segment
        if (segmented[i + 1] === '.' && (segmented[i + 2] === '/' || i + 2 === segmented.length)) {
          output.pop();
          i += 2;